Circuit module and method of manufacturing the same

ABSTRACT

Manufacturing method and circuit module, which comprises an insulator layer and, inside the insulator layer, at least one component, which comprises contact areas, the material of which contains a first metal. On the surface of the insulator layer are conductors, which comprise at least a first layer and a second layer, in such a way that at least the second layer contains a second metal. The circuit module comprises contact elements between the contact areas and the conductors for forming electrical contacts. The contact elements, for their part, comprise, on the surface of the material of the contact area, an intermediate layer, which contains a third metal, in such a way that the first, second, and third metals are different metals and the contact surface area (A CONT 1 ), between the intermediate layer and the contact area is less that the surface area (A PAD ) of the contact area.

TECHNICAL FIELD

The present invention relates to circuit modules, which comprise aninsulator layer and, inside the insulator layer, at least one component,which comprises contact areas. In addition, the circuit modules compriseconductors on the surface of the insulator layer, through which acomponent can be connected to become part of a circuit outside thecomponent. For creating electrical contacts, the circuit modulescomprise contact elements between the contact areas of the component andthe conductors.

The invention also relates to methods for manufacturing theaforementioned circuit modules.

BACKGROUND ART

In the background art, several different ways are described, by means ofwhich circuit modules containing components located inside an insulatormaterial can be manufactured. The background art also discloses severalsolutions for manufacturing electrical contacts to the contact terminalsof a component, by means of contact elements, and methods formanufacturing a conductor-pattern layer connected to the contactelements.

When evaluating circuit modules and manufacturing methods, attention canbe paid, for example, to the circuit module's properties achieved by themethod, for example, its price, mechanical durability, and the thickness(thinness) that can be achieved. Depending on the applications,significant factors can also be the quality and durability of theelectrical contacts and the reliability and quality of the electricalproperties of the whole module. Significant properties to be examined interms of manufacturing can also be, for example, the reliability, yield,efficiency, price, and environmental friendliness of the manufacturingmethods to be used. The practicability of the manufacturing method isalso affected by the availability of raw materials and the ability ofthe method to place different types of component in a circuit module.

All in all, the requirements set for manufacturing methods and circuitmodules are thus very diverse and vary according to the application.This being the case, there is still a need in the sector to develop newcircuit-module structures and manufacturing methods, which can offer newor improved properties, or combinations of properties.

One line of development has been the placing of components inside theelectronics module in a bumpless form, i.e. without growing bumps of topof the contact areas of the component. Cost benefits can then be gained,as the components need no longer be transported during manufacture to aseparate production plant to make the bumps.

The applicant's own patent and application publications disclosemanufacturing techniques, which can also be used in connection withbump-free components. The techniques described are particularly suitablefor components, in which the material of the contact areas is copper. Ofthe applicant's own publications, those that can be referred to as mostclosely relating to the invention are the international patentapplication publications WO 2004/089048, WO 2005/027602, WO 2005/125298,WO 2006/013230, WO 2006/056643, WO 2006/134216, WO 2006/134217, and WO2007/107630.

However, at present copper is quite little used as a conductor materialin semiconductor processes. The most common conductor material isaluminium. In circuit-board manufacture, on the other hand, copper isthe principal material for conductors. Copper conductors of a circuitmodule can be grown directly on top of aluminium contact areas, but thecontact between copper and aluminium is brittle, so that a module ofthis kind is not optimal in applications, in which mechanical stressacts on the circuit module.

An improved possibility to use contact areas of aluminium or contactareas containing aluminium would mean that, in circuit modules andmanufacturing methods, normal semiconductor circuits in a bumpless formcould be used immediately after the semiconductor manufacturingprocesses and the passivation of the surface. As aluminium is theconductor material most widely used in the semiconductor industry, goodcompatibility between the contact element of the circuit module andaluminium would also ensure that suitable semiconductor circuits wouldbe abundantly and economically available. Attempts to develop suchmanufacturing methods have indeed already been made for several decadesin the field of component packaging technology. In component packagingsolutions of this kind, the goal has been a technique, by means of whicha relatively small component package could be manufactured around acomponent, to which a circuit board could then be attached later. Unlikepackaging technology, the goal of the manufacturing techniques of thecircuit module to which the present invention relates is the ability tomanufacture the entire circuit board in the same process, so as tocompletely eliminate the packaging stage of the separate component. Ofcourse, this does not exclude the possibility of using the manufacturingmethod of the circuit module to manufacture only a component package.

The patent U.S. Pat. No. 4,246,595, Noyori et al., discloses a method,in which the contact areas of a component are brought into contact withan insulator sheet, in which V-shaped openings have been made. First ofall, a layer of titanium (Ti) or chromium (Cr) is grown on the surfacesof the openings and the aluminium contact areas. This intermediate metallayer is intended to prevent the copper from diffusing into thealuminium and the semiconductor component, as well as to improve theadhesion between the copper and the aluminium. In addition, theintermediate layer acts as an electrical conductor later duringelectrochemical growing (electroplating), so that the intermediate metallayer will reliably cover also the side walls of the openings. Thegrowing of the titanium or chromium layer requires the use of thesputtering technique, for which reason the openings must also have aclear V shape. Sputtering is expensive when used on large surfaces (oncircuit modules) while additionally the open V shape reduces theavailable conducting density. Contract structures of a correspondingtype are also disclosed in patents U.S. Pat. No. 4,783,695 and U.S. Pat.No. 4,894,115, Eichelberger et al., and in patent U.S. Pat. No.5,353,195, Fillion et al.

Later, in patent U.S. Pat. No. 6,396,148, Eichelberger at al., anattempt is made to solve the problems relating to sputtering, by formingthe intermediate metal layer by growing a layer of nickel on the surfaceof the aluminium contact areas. According to the patent, the growing ofthe nickel is performed by means of a chemical growing method(electroless plating). Yet another layer, which also covers the sidewalls of the openings made in the insulating material for the contacts,is growing on top of the nickel layer by means of a chemical growingmethod. In the method, the components are attached firs by their sideand rear surfaces to the insulator layer and, after this, aphoto-patternable polymer is spread on the front surface of thecomponent and on top of the contact areas. The polymer is patterned byexposing it to light and developing it, to form openings for thecontacts.

One possibility is to grow bumps on the surface of the conductors of thecircuit-board part of the circuit module and attach the component to theconductors by a flip-chip mounting technique, for example, by ultrasoundbonding. Such a method is disclosed in the applicant's own internationalpatent application WO 2006/134220. Problems relating to both productionand the quality of the contacts are associated with methods using flip-chip methods.

DISCLOSURE OF INVENTION

The object of the invention is to develop a new contact-elementstructure envisaging the utilization of bumpless components, as well asa circuit module and manufacturing technique using such a structure.

According to an aspect of the invention, a bumpless component is used inthe circuit module, the material of the contact areas of which being ofa different metal, or metal alloy to the conductors of the conductorlayer of the circuit module. The contact areas of the component and theconductors of the circuit module are connected to each other with theaid of contact elements, which contain an intermediate layer, whichcontains a third metal or metal alloy, which differs from the materialof the contact areas and conductors, on the surface of the material ofthe contact area. In addition, the contact surface area between theintermediate layer of each contact element and the contact area of thecomponent is smaller that the surface area of the contact area.

According to another aspect of the invention, a manufacturing method iscreated in order to manufacture the circuit module described above, inwhich the component is attached to a conductor foil or conductor-patternlayer with the aid of a polymer layer and contact elements are madethrough the polymer layer. When making the contact elements, contactholes are made in the polymer layer on top of the contact areas, at thelocations of the contact areas. The contact holes are dimensioned insuch a way that the contact surface area between each contact hole andthe corresponding contact area is smaller than the total surface area ofthe contact area. After this, the contact holes are filled with aconductor material, in such a way that filling is started by coating thesurface of the contact areas with an intermediate layer, for example, byusing one or more chemical metal-growing methods.

Thus, a new type of circuit module and manufacturing method is obtained,which can offer some advantages in terms of the applications of somecircuit modules.

In addition, the invention has numerous special embodiments, whichprovide additional advantages.

In one embodiment, components are used in the circuit module, thematerial of the contact areas of which contains aluminium and thecontact elements comprise a layer containing zinc on the surface ofthese contact areas containing aluminium. In addition, the contactelements are manufactured in such a way that the contact surface areabetween the layer containing zinc and the contact area is smaller thanthe total surface area of the actual contact area.

A layer containing zinc has been observed to be useful in terms of thequality of the electrical contact, as coating a layer containing zinc onthe surface of an aluminium contact area prevents the re-oxidation ofthe aluminium surface and permits the creation of good adhesion betweenthe aluminium and the next layer. In addition, the layer containing zincimproves the mechanical durability against lateral stress of the contactformed through the interface between the aluminium and the intermediatelayer of other metal.

We have observed that extremely good mechanical durability is achievedby using a double zincate process, in which the blank containing thecomponents is subjected to the zincate process at least twice. Thus amore even and denser layer of zinc is made to grow on top of thealuminium contact surfaces. After a single zincate treatment, there iszinc on only some areas of the contact surfaces, or else the layer isporous, therefore a double zincate process is used in the preferredembodiment.

The possibility to use contact elements that are narrower than thecontact area can, for its part, provide advantages, for example, byallowing the conductors connected to the contact elements to also bemade narrow, especially in embodiments, in which the contact element isessentially of even width vertically, or only narrows moderately towardsthe component.

In an embodiment of the manufacturing process, in which contact openingsare made in the conductor foil of the conductor-pattern layer prior toattaching the component, the component can be attached aligned relativeto the contact openings while, in addition, the contact holes needed forthe manufacture of the contact elements can be made through thesecontact openings, by using the material of the conductor foil orconductor- pattern layer as a mask. In such an embodiment, an advantageis obtained in the case of the alignment between the contact elementsand the contact areas. In addition, an advantage is obtained in terms ofthe manufacture of the contact holes, because the holes can be openedusing a CO₂ laser, for example.

In an embodiment, in which the contact holes are opened using a laser,the contact holes can be opened one component or component-group at atime, and thus the first intermediate layer can be manufactured firstthrough the contact holes, on top of the contact areas of the firstcomponents, and then later the second intermediate layer can bemanufactured through the contact holes opened later, on top of thecontact areas of the second components. Thus, components, the materialsof the contact areas of which differ from each other and areincompatible with the growth processes of the same intermediate layer,can be fitted in the same process.

In the embodiments, it is also possible to attach the components to theconductors by means of mutually differing polymer layers. Thus theproperties of the insulation between the component and the conductor canbe arranged to also be suitable for different mechanical and electricalrequirements.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1-8 show the intermediate stages of a circuit module when using amanufacturing method according to one embodiment.

FIG. 9 shows one example of a circuit module according to oneembodiment.

FIGS. 10-17 show the intermediate stages of a circuit module when usinga manufacturing method according to a second embodiment.

FIGS. 18-23 show the intermediate stages of a circuit module when usinga manufacturing method according to a third embodiment.

FIG. 24 shows one intermediate stage of a circuit module when using amanufacturing method according to a fourth embodiment.

FIG. 25 shows one possible example of a contact hole and its dimensionsmade for a contact element of a circuit module.

FIG. 26 shows examples of possible contact holes.

FIG. 27 shows some embodiments of intermediate layers manufactured inthe contact hole of FIG. 26.

FIG. 28 shows one contact-element structure.

FIG. 29 shows a second contact-element structure.

FIG. 30 shows a third contact-element structure.

FIG. 31 shows a fourth contact-element structure.

FIG. 32 shows a fifth contact-element structure.

FIG. 33 shows a sixth contact-element structure.

MODES FOR CARRYING OUT THE INVENTION

FIGS. 1-9 show one exemplary application of the manufacturing methodaccording to one embodiment. In this embodiment, manufacture begins froma conductor foil 12, which of metal, for example. A suitable conductorfoil 12 is, for example, a copper film, the thickness of which is in therange 1-70 μm, typically in the range 3-12 μm. Instead of a bareconductor foil 12, it is also possible to use as the base material alayered sheet, which comprises a conductor foil 12 and an insulatorlayer 13, which is shown by a broken line in FIG. 1, on the surface ofthis. In the embodiments described in the following, it is possible touse such a layered sheet 12, 13, in place of the conductor foil 12.

Differing from what is shown in FIG. 1, it is also possible to use alayered sheet, which comprises a support membrane on the second surfaceof the conductor foil 12. The support membrane is on the oppositesurface of the conductor foil relative to the components to be attachedto the conductor foil. If the layered sheet also comprises an insulatorlayer 13, the support membrane will then be on the opposite side of theconductor foil to the insulator membrane 13. The support membrane can beused, for example, to improve the mechanical stiffness and ease ofhandling at the start of the manufacturing process of the conductor foil12, or the layered sheet 12, 13. The support membrane is, however,intended to be removed at a later stage in the process. It is alsopossible to proceed by starting manufacture from a support membranewhile a conductor foil 12, which is patterned or unpatterned, is made onthe surface of this. The process examples and stages described in theapplication example can also be performed correspondingly when using asupport membrane, though this is not stated separately. In thedescription hereinafter, however, reference will be made to a supportmembrane only when calling attention to something particularlynoteworthy in the case of an embodiment using a support membrane. Theactual support membrane can be, for example, of an electricallyconductive material, such as aluminium (Al), steel, or copper, or aninsulating material, such as a polymer. The thickness of the supportmembrane can be, for example, 25-400 μm. The thickness of the supportmembrane is typically in the range 35-105 μm.

Next, contact openings 8 are made in the conductor foil 12, which arelocated on the conductor foil 12 in such a way that they are placed atthe positions of the contact terminals of the components being placed inthe module being manufactured. Thus, an individual contact opening 8 ismade in the conductor foil 12 for each contact terminal of thecomponent. In this embodiment, the contact openings 8 can bemanufactured with the aid of a UV laser. The contact openings 8 can alsobe manufactured, for example, mechanically by drilling, milling, oretching. In an embodiment using a support membrane, the contact openings8 are preferably made from the direction of the opposite surface, insuch a way that they penetrate the conductor foil 12 completely.However, the contact openings need not penetrate the sheet, instead themethod can equally well also be designed in such a way that the contactopenings 8 only extend as far as the surface of the material of thesupport membrane, or form recesses in the material of the supportmembrane, without, however, passing entirely through it. Also, thecontact openings need not pass entirely through the conductor foil, if athick conductor foil is used, which is thinned by etching in a laterstage.

In the embodiment of FIG. 1, the contact openings 8 are manufactured insuch a way that the size of a contact opening 8 is less than the contactsurface area of the contact material to be placed at the opening 8. Thecontact opening is typically circular in shape, though other shapes toocan be used. The shape and size of the contact opening 8 are selected insuch a way that the contact surface of the contact terminal can coverthe contact opening 8 entirely.

According to FIG. 2, manufacture is continued by spreading adhesivelayers 5 on the surface of the conductor foil 12, in the connectionareas of the components. The adhesive layers will then also cover thecontact openings 8. Alternatively, the adhesive 5 can be spread on thesurface of the components. The adhesive can also be spread on thesurface of both the component and the conductor foil 12. Typically, theadhesive is spread locally, so that the adhesive layers 5 will belocated only in the connection areas of the components.

The term adhesive refers to a material, by means of which the componentscan be attached to the conductor foil 12 or insulator layer 13 that actsas a base. One property of the adhesive is that the adhesive can bespread on the surface to be glued in a relatively fluid form, or onethat otherwise conforms to the surface shapes, for example, in the formof a film. A second property of the adhesive is that, after spreading,the adhesive hardens, or can be hardened, at least partly, in such a waythat the adhesive is able to hold the component in place (relative tothe conductor foil 12) at least until the component is secured to theconstruction in some other way. A third property of the adhesive is anadhesive capability, i.e. an ability to stick to the surfaces beingglued.

The term gluing, for its part, refers to the attachment of pieces to beglued to each other with the aid of an adhesive. In the embodiments, theadhesive is brought between the component and the conductor foil 12 orinsulator layer 13 acting as a base and the component is placed in asuitable position relative to the base, in which the adhesive is incontact with the component and the base and at least partly fills thespace between the component and the base. After this, the adhesive isallowed (at least partly) to harden, or the adhesive is (at leastpartly) actively hardened, so that the component attaches to its basewith the aid of the adhesive. In some embodiments, the contactprotrusions of the component may protrude during gluing through theadhesive layer to come into contact with the base.

The adhesive used in the embodiments is typically an epoxy-basedadhesive, for example a heat-cured epoxy adhesive. The adhesive isselected in such a way that the adhesive to be used will have sufficientadhesion to the base and the component. One preferred property of theadhesive is a suitable coefficient of thermal expansion, so that thethermal expansion of the adhesive will not differ too much from thethermal expansion of the surrounding material during the process. Itwould also be preferable for the adhesive selected to have a shorthardening time, preferably of a few seconds at most. Within this time,it would be good for adhesive to harden at least partly, so that theadhesive can hold the component in place. Final hardening can take aclearly longer time and can even be planned to take place in connectionwith later process stages. In addition, the stresses caused by the laterprocess stages, such as thermal, chemical, or mechanical stress, aretaken into account when selecting the adhesive. The electricalconductivity of the adhesive will be preferably in the order of theelectrical conductivity of the insulator materials.

Next, components 6 and 16, which comprise contact terminals 7 and 17,are taken. Both components 6 and 16 are semiconductor components, forexample, processors, memory chips, or other microcircuits. The contactterminals of the component 6 are contact areas 7, which are locatedessentially on the level of the surface of the component. Such contactareas 7 of the component 6 are created at the semiconductor factoryduring the manufacturing process of the semiconductor component. Thecontact area 7 typically forms the surface of a conductor pattern on themetal used in the process. The metal used in the manufacturing processof semiconductor components is typically aluminium, though other metals,metal alloys, or other conductor materials can also be used. Forexample, the use of copper has become common in semiconductor-componentmanufacturing processes.

The contact terminals of the component 16 are contact bumps 7, whichprotrude from the level of the surface of the component. Such contactbumps 17 are manufactured in a bump-making process after the manufactureof the semiconductor component 16, typically in a separate factory. Thecontact bump 17 can contain one or more metals, metal alloys, or otherconductor materials. Typically, the outer surface of the contact bump17, i.e. the contact surface, is made from copper or gold.

The components 6 and 16 are aligned relative to the contact openings 8,in such a way that each contact terminal 7, 17 comes next to thecorresponding contact opening 8, and is pressed against the adhesivelayer 5. After this, the adhesive is at least partly hardened, so as toprevent, or minimize the relative movement of the components 6, 16 andthe conductor foil 12 after alignment. In alignment and gluing, the aimis to position the contact opening 8 to be in the centre of thecorresponding contact terminal 7, 17.

After this, insulator sheets 11, in which openings are made for thecomponents 6, 16, as well as a unified insulator sheet 10, which is ofunhardened or pre-hardened polymer, are laminated on top of theconductor foil 12. During lamination, the insulator sheets 10, 11 aremelted together and form a unified insulator layer 1 around thecomponents 6, 16. In the embodiment of FIG. 2, the insulator sheets 11are fibre mats impregnated with polymer, or sheets containingpre-hardened polymer and reinforced with a fibre material.

The polymer can be, for example, epoxy and the fibre reinforcement canbe, for example, glass-fibre mat. A typical example of a suitableinsulating-sheet 11 material is an FR4-type glass-fibre reinforced epoxysheet. Other reinforcement and polymer material combinations can beused, of course. When using several insulator sheets 11, the sheets canalso differ mutually.

In FIGS. 2 and 3, the fibre material is shown by wavy shading 19. In thefigures hereinafter, the fibre material 19 is not shown, but thesestructures too include fibre material 19. The fibre material 19contained in the insulator sheet 11 or the insulator sheets 11 acts as areinforcement, which provides the electronic module being manufacturedwith mechanical strength. According to the example of FIG. 2, holes 4are made in the insulator sheets 11 at the locations of the components6, 16. The insulator sheets 11 are perforated particularly to makeopenings for components in the fibre material 19 contained in theinsulator sheets 11. Without perforation, the components would pressagainst the fibre-material layers 19 during lamination. The unperforatedinsulator sheet 10, on the other hand, can be fibre-reinforced orunreinforced, depending on the embodiment.

The insulator sheets 10, 11 are typically selected in such a way thatthey contain enough fluid polymer for the polymer flowing in thelamination stage to be sufficient to fill the holes 4 made in theinsulator sheets 11 for the component 6, 16, around the components. Thestructure shown in FIG. 3 is then obtained, in which the insulator layer1 contains a tight polymer layer, which contains one or morereinforcements of a fibre material 19. The polymer layer is boundtightly to the fibre layer 19 while the tight polymer layer alsoattaches the components 6, 16 to the surfaces, so that a tight, unified,and mechanically strong insulator layer is formed, which contains thecomponents 6, 16, and which is, in addition, reinforced with fibrematerial 19.

In the example of FIG. 2, a unified insulator sheet 10 is used, thoughthe insulator sheet 10 can also be omitted from the structure. In thatcase, the insulator sheet 11 or insulator sheets 11 are selected in sucha way that they themselves already contain sufficient fluid polymer tofill the holes 4 in the insulator sheets 11 around the components 6, 16.However, it is typically easier to ensure the filling of the holes 4 byusing a separate insulator sheet 10.

A conductor foil 14, which is preferably of a material that is similarto, and equally as thick as the conductor foil 12, is also laminatedwith the insulator sheets 10, 11 into a single structure. Thus, theinsulator layer 1 and the components 6, 16 remains between thecorresponding conductor foils 12 and 14. FIG. 3 shows this intermediatestage of the module manufacture. In the intermediate stage of FIG. 3,there is adhesive on the contact surface of the contact terminals 7, 17and typically also in the contact openings 18. In the stage shown inFIG. 4, this adhesive is removed and contact holes 18, which extend tothe contact surfaces of the contact terminals 7, 17 are formed at thepositions of the contact openings 8.

With reference to FIG. 3, it can be further stated that the structurecan also be manufactured in such a way that a unified layer of fibrematerial 19 runs between the components 6, 16 and the conductor foil 14.Such a construction can be used when the thickness of the components 6,16 is sufficiently less than the thickness of the insulator layer 1. Thestructure can be manufactured, for example, in such a way that a unifiedinsulator sheet 10, which contains the fibre material 19 of the layer,can be laminated onto the structure.

If a support membrane is used in the embodiment on the surface of theconductor foil 12, as depicted in connection with the description ofFIG. 1, it is most suitable to remove the support membrane after thelamination, i.e. between the intermediate stages shown in FIGS. 3 and 4.

After lamination and the removal of the possible support layer, theadhesive layer, which has been created in the contact openings 8 andbetween the contact openings 8 and the contact terminals 7, 17, isremoved. In the embodiment of the figures, the removal of the adhesiveis implemented by the laser-ablation method, using a CO₂ laser. Theability of a CO₂ laser to vaporize organic insulating substances, suchas epoxy-base adhesive, is good, but its ability to vaporize copper orother metals is poor, to that the conductor foil 12 can be used as maskfor making the contact holes 18. Thus, it is possible to manufacturecontact holes 18, the diameter of which is less than the diameter of thebeam of the CO₂ laser. This property creates a significant advantage, asthe minimum diameter of the beam of a CO₂ laser is typically in theorder of 75 μm, which is too large when considering the manufacture ofprecise electronic module structures. A UV laser, on the other hand, cantypically be used to manufacture clearly more precise structures. Theminimum diameter of the beam of a UV laser can be, for example 25 μm,but a UV laser is not, on the other hand, suitable for removing adhesivefrom the contact openings 8 and from between the contact openings 8 andthe contact terminals 7, 17.

Thus, the use of a conductor mask permits the manufacture of veryprecisely limited and precisely positioned contact holes 18 in aninsulator material, such as the adhesive 5 using in the embodiment. Inaddition, the use of a CO₂ laser permits the cleaning of the contactsurfaces of the contact terminals 7, 17 in the same process stage,without any significant danger of destroying or damaging the contactterminals 7, 17. In the embodiment, the conductor foil 12 is of copperwhile the contact terminals 7, 17 of the component are also of metal, sothat they are not sensitive to the beam of the CO₂ laser, so that theprocess can be designed in such a way that the contact surfaces of thecontact terminals 7, 17 will be sure to be cleaned sufficiently well.Thus, the advantage of the method described is that contact openings 8can be made in the conductor foil 12 very precisely with the aid of a UVlaser and, after this, the contact openings can be used as a mask forthe making of the contact holes 18 by means of a CO₂ laser that is lessprecise, but safer for the structure.

If the contact holes 8 of the conductor foil 12 were to be manufacturedonly in this process stage, the method used for machining the metal ofthe conductor foil 12, for example, a UV laser, would more easily damagealso the contact terminals 7, 17, because the energy required topenetrate the conductor foil 12 is significantly greater than the energyrequired to penetrate the adhesive or other insulation between thecontact terminals 7, 17 and the conductor foil 12. In such amanufacturing method, it would be challenging to stop the drilling atprecisely the correct depth. In addition, aligning the drilling would bemore difficult, due to the deformations arising during lamination andfor the reason that the contact terminals 7, 17 of the components cannotbe seen through the solid metal film. The use of contact holes 8pre-manufactured in the conductor foil 12 provides significantadvantages, both in the alignment of the components 7, 17 and in themanufacture of the contact holes 18.

In FIG. 5, an intermediate layer 2, which is of a suitable conductormaterial, is made in the contact holes 18. The intermediate layer 2 ismanufactured using a suitable chemical conductor-material growing method(electroless plating). The intermediate layer 2 can also consist of alayer of two or more different materials, which are manufacturedcorrespondingly using two or more methods. One purpose of theintermediate layer 2 is to form a conductor membrane for the side wallsof the contact holes 18, which connects the contact terminals 7, 17 andthe conductor foil 12 to each other. A second purpose of theintermediate layer 2 is to provide a material adapter between thematerial of the of the contact terminals 7, 17 and the conductor-patternmaterial to be connected to them. Such a material adapter can berequired, for example, in order to ensure the quality of the mechanicalor electrical contact and durability, for example, when the material ofthe conductor-pattern layers of the circuit module is copper and thematerial of the contact terminals 7, 17 is something other than copper(Cu), for example aluminium (Al).

When manufacturing the intermediate layer 2, a suitable chemical growingmethod is used, because by means of such a method the conductor materialcan also be grown on the vertical surfaces of the contact holes 18,unlike when using sputtering, for example.

An electrochemical method (electroplating) cannot be used in this stage,because the side walls of the contact holes 18 are not conducting.Alternatively, V-shaped-opening contact holes can be used and theintermediate layer 2 made by sputtering. Sputterable materials suitablefor this purpose are, for example, titanium-wolfram (TiW) and chromium(Cr). A layer of nickel (Ni) and gold (Au) ca also be grown on top ofthe TiW or Cr layer. In the example of FIG. 5, nickel frown by achemical method is used as the intermediate layer 2 in the example ofFIG. 5, however, so that the intermediate layer 2 will grow at the sametime also on the surfaces of the conductor foils 12 and 14. Anotherexample of the intermediate layer 2 is a layer containing zinc,manufactured on the surface of the contact terminals 7, 17, on top ofwhich a layer of nickel (Ni) can further be manufactured. Morealternatives that are possible are depicted in connection with thedescription of FIGS. 26-33.

In this embodiment, after the manufacture of the intermediate layer 2,manufacture is continued by spreading resist layers 3, typicallyphotoresist layers, on both surfaces of the module. The resist layers 3are patterned with the aid of a conductor-pattern mask by exposure anddevelopment, in such a way that the resist 3 is removed from the desiredparts of the conductor patterns of the conductor-pattern layers. Thisintermediate stage is shown in FIG. 6. After this, the module is takento an electrochemical bath and voltage is led to the intermediate layers2 of the module. The desired conductors of the conductor-pattern layerare then grown in the openings of the resist layers 3. The conductormaterial also grows in the contact holes 18, forming a conductor core tothe contact elements, as can be seen from FIG. 7. In the example of FIG.7, the conductors 22, 24 are electrochemically grown copper. Finally,thin etching-mask layers are grown on the surface of the conductors 22,24. A layer of tin (Sn), for example, can act as the etching mask.

Next, the resist layers 3 are removed, when, in the embodiment of thefigures, the intermediate layer 2 is revealed from under the removedresist. The revealed part of the intermediate layer 2 is removed, forexample, by etching, the same procedure being use for the parts of theconductor foils 12 and 14 revealed outer the conductors 22 and 24. Theetching-mask layer then protects the outermost surfaces of theconductors 22 and 24 from the effects of the etching. An electronicmodule, which contains two components 6 and 16 connected electrically toconductors 22, comprising two conductor-pattern layers (conductors 22and 24), and shown in FIG. 8, is then obtained.

In the example of FIGS. 6 and 7, the conductors 22 and 24 are growndirectly into their correct shape in the openings made in the resistlayer 3. However, the conductors 22 and 24 can also be manufactured inanother way, both in this example and in the examples describedhereinafter. One alternative way of manufacture is to grow a unifiedlayer of conductor material over the surfaces of the entire module blankand to pattern the conductor layer later by means of a lithographymethod, in order to form the conductors 22 and 24. Described in greaterdetail, it is possible to proceed, for example, in such a way that,continuing from the intermediate stage of FIG. 5, copper is grown on thesurfaces of both intermediate layers 2 by means of an electrochemicalmethod. In that case, the contact holes 18 too are filled with copper.After this, resist layers are spread on top of the copper layers, theresists are patterned, and the excess parts of copper, or theintermediate layer 2 and the conductor foils 12 and 14 are etched. Afterthis, the resist mask is removed. Using either manufacturing method, theresult is the structure shown in FIG. 8.

FIG. 8 can show an already finished simple circuit module, butmanufacture is usually continued by manufacturing additional insulatorand conductor layers on the surfaces of the circuit module, which areconnected electrically with the aid of vias to the structure shown inFIG. 8. In addition, it should be noted that vias can be manufactured inthe module too of FIG. 8, which connect the conductors 22 to theconductors 24. Such vias can be manufactured in a corresponding mannerto, and in the same process stages as described above in the manufactureof the contact elements.

The module of FIG. 8 can be further refined in the manner shown in FIG.9, in such a way that the surfaces of the module are protect byprotecting layers 20. In addition, in the example of FIG. 9, externalcontact elements, which comprise bases 21 made on top of the conductorpatterns 22, 24 and contact balls 23 made on their surfaces, aremanufactured in the module.

FIGS. 10-16 show a manufacturing method according to a secondembodiment, up to a stage corresponding to the intermediate stage shownin FIG. 5. Manufacture can be continued from the intermediate stage ofFIG. 16, for example, as shown by FIGS. 6-9, or suitably also in analternative manner, in which the material of the conductors 22 and 24 isfirst of all grown over the entire surface and after that patterned toform conductors 22 and 24. The technical features and parameterspresented in connection with the description of FIGS. 1-5 can also beapplied in the process stages shown in FIGS. 10-16, so that there is noneed to repeat all the details of the manufacturing process and theiradvantages in the following embodiment. On the other hand, the essentialdifferences between the embodiments shown by FIGS. 1-9 and FIGS. 10-16are brought out in the following.

In the embodiment of FIGS. 10-16, manufacture starts, as in FIG. 1, froma conductor foil 12, in which contact openings 8 are made. After this, aspacer 15 is attached to the future attachment point of the component 6on the surface of the conductor foil 12. The spacer 15 is of a suitableinsulating material, for example, of pre-hardened adhesive or some otherpolymer, which has sufficient adhesion with the surface of the conductorfoil 12. The spacer 15 can also be of hardened polymer, in which case itcan be attached to the surface of the conductor foil 12, for examplewith the aid of separate adhesive.

A spacer 15 can be used for many different reasons. One use of a spaceris to increase the insulating thickness between the component 6 and theconductor foil 12. The need to increase the insulating thickness can beimposed, for example, by the requirements set by the electricaloperation of the circuit module or the component 6. In that case, withthe aid of the spacer 15 it is possible to set the properties of theinsulation between the component 6 and the conductor foil 12 as desired.The properties selected can be, for example, a desired specificresistance and spark-over resistance, which can be influenced by theselection of the material of the spacer 15 and the adhesive 5. Thespacer can also be used to prevent a short-circuit between the componentand the conductor foil 12. Such a use will come into question especiallyin embodiments in which the surface of the component 6 is pressed veryclose to the conductor foil, when a risk arises of unintended electricalcontacts being formed between the conductor structures on the surface ofthe component and the conductor foil. A spacer can also be used toweaken the capacitive connection between the internal circuit elementsof the component 6 and conductors 22 running next to the location of thecomponent 6.

In addition to, or instead of a spacer 15, it is possible to use for thesame purpose an insulator layer 13 entirely covering the surface of theconductor foil 12, as described in connection with FIG. 1.

In the examples of FIGS. 10-16, a spacer 15 is used in connection with abumpless component 6, but the contact terminals of a component 16 withbumps must be made to extend closer to the surface of the conductor foil12, so that a sufficient insulating gap can be ensured between theopposite surface of the component 16 and the conductor foil 14. In theembodiment, spacers 15 selected component-specifically can be placed inthe circuit module, in order to optimize the electrical and/ormechanical properties of the circuit-board module. The same module canthus also contain different kinds of spacers 15 and thus spacers 15 canalso be used in series production, in order to make components 6, 16coming from different sources and with different properties to eachother compatible with the circuit-board manufacturing process beingused. One example of a mechanical property requiring optimization is thethickness of the insulator layer 1 (and at the same time of the entiremodule), which can be reduced with the aid of suitable selected spacers15, which can be seen, for example, in FIG. 12.

According to FIG. 11, manufacture is continued by spreading adhesivelayers 5 on the surfaces of the conductor foil 12 and the spacer 15 inthe connection areas of the components. The components 6 and 16 arealigned relative to the contact openings 8 and glued in place. Afterthat, in the example of FIG. 11, insulator sheets 10, 11 and a conductorfoil 14 are laminated on top of the conductor foil 12. Next,photo-resist layers 30, which are patterned in such a way that openingslarger than the contact openings 8 are created at the positions of thecontact openings 8, are spread on the surface of the conductor foils 12and 14, or a coating is made electrophoretically on top of the entireconductor layer. This photo-resist layer 30 is used to limit the growthof an intermediate-layer material grown using a non-selective method tothe contact holes and the immediate surroundings of the contact openings8. Such a procedure can also be used in connection with the exampledescribed above, nor, on the other hand, is it essential in the examplesof FIGS. 10-16. FIG. 12 shows the module after these stages. The contactterminals 7 of the component 6 are covered by both a spacer 15 andadhesive 5. There is adhesive on the surface of the contact bumps 17 ofthe component 16 and in the corresponding contact openings 8.

In the stage shown in FIG. 13, contact holes 18 are made at thepositions of the contact openings 8 of the component 6. The contactholes are opened through the spacer 15 and the adhesive layer 5, as faras the contact surfaces of the contact terminals 7. In the embodiment ofthe figure, the opening of the contact holes 8 is implemented by thelaser-ablation method, using a CO₂ laser, as described in connectionwith FIG. 4. In the embodiment of FIGS. 10-16, the important fact isthat contact holes are not opened at this stage of the position of thecontact terminals 17 of the second component 16.

In the stage shown in FIG. 14, an intermediate layer 2, which is of asuitable material, is made in the contact holes 18 of the component 6.The conductor material of the intermediate layer 2 is selected on thebasis of the material of the contact terminals 7 of the component 6 andmanufactured using a suitable chemical conductor-material growingmethod. In the example of the figure, the material of the contactterminals 7 of the component is aluminium and the material of theintermediate layer 2 is mainly a metal alloy containing zinc. Theprinciples described in connection with FIG. 5 above are applied to thegrowing of the intermediate layer. Unlike the example of FIG. 5, in thecase of FIG. 14, it is, however, also possible to proceed in such a waythat in this stage the intermediate layer 2 is grown with the aid of aselective method only on the surface of the contact terminals 7, i.e. onthe bottom of the contact holes 18 and not on the edges of the contactholes 18. In this embodiment, the intermediate layer 2 coming on theedges of the contact holes 18 is grown later in connection with thegrowing of the intermediate layer relating to the contact bumps 17 ofthe component 16. The embodiment using a selective growing method hasthe advantage that the intermediate layer 2 does not grow on top of theadhesive layer covering the contact bumps 17 of the component 16.

Manufacture is continued in the stage shown in FIG. 15 by manufacturingcontact holes 28 at the positions of the contact openings 8 of thesecond component 16. After this, the module according to FIG. 16 issubjected to a suitable chemical conductor-material growing method. Inthe example of FIG. 15, the growing method in non-selective and theconductor material grows on all the free surfaces of the module and thusalso in the contact holes 18 of component 6 and in the contact holes 28of component 16. However, the photo-resist layer 30 protects thesurfaces of the module, so that the intermediate layer 2 grows only inthe contact holes 18 and 28 and in their surroundings. After this, thephoto-resist and the conductor material that may have grown on itssurface is removed. Such an embodiment using a photo-resist layer 30 canbe useful, for example, when nickel or some other metal differing fromcopper is grown in the openings of the photo-resist layer, for example,using a non-selective method. The conductors 22 and 24 can then bemanufactured to consist of solely a copper layer.

In other embodiments, suitably selected selective growing methods canalso be used and the conductor material frown only on the surfaces ofthe contact bumps 17 of the component 16, correspondingly as describedabove in connection with FIG. 14. In any case, at this stage theintermediate layer 2 is grown at least on the surfaces of the contactbumps 17 of the component 16 and on the surfaces of the side walls ofthe contact holes 28 and, in addition, if desired also on the surface ofthe intermediate layer 2 connected to the contact terminals 17 of thecomponent 6 and/or on the surfaces of the side walls of the contactholes 18 of the component 6.

If the example of FIGS. 10-16 were to be implemented without the use ofa photo-resist 30, in the example of FIG. 16 the material of the surfaceof the contact bumps 17 of the component 16 could suitably also becopper and the material of intermediate layer 2 to be grown of thesurface of the contact bumps 17 would then be copper manufacturedsuitably using a chemical growing method.

After the manufacture of the intermediate layer 2, in this embodimentmanufacture can be continued, for example, in the manner stated inconnection with the description of FIGS. 6-9, by manufacturing conductorpatterns on the surface of the module and conductor cores for thecontact elements located in the contact holes 18 and 28.

Another alternative is to coat copper on both conducting surfaces of themodule, after the removal of the photo-resist layer 30. After this, thecopper layers can be patterned to form conductors 22 and 24, when thestructure shown in FIG. 17 will be obtained, in which the conductors 22and 24 are formed of the first and second copper layers in thesurroundings of the contact elements, as well as of an intermediatelayer 2, which is of nickel for example, between them. Elsewhere, theconductors 22 and 24 are formed of a first and second copper layer,between which is the interface to be analysed. Once the structure ofFIG. 17 has been manufactured, it is possible, if desired, to continuein some manner described in connection with any of the previousexamples.

FIGS. 18-23 show a manufacturing method according to a third embodiment,which is a variation of the embodiment shown in FIGS. 10-16. From theintermediate stage of FIG. 23, manufacture can be continued, forexample, in the manner shown in FIGS. 6-9. The technical features andparameters presented in connection with the description of FIGS. 1-5 and10-16 can thus also be applied in the process stages shown in FIGS.18-23, to that all the details and their advantages of the manufacturingprocess need not be unnecessarily repeated in the following embodiment.However, in the following the essential difference between theembodiments shown in FIGS. 10-16 and FIGS. 18-23 is presented.

In the embodiment of FIGS. 18-23, manufacture is commenced, as in thecase of FIG. 10, from a conductor foil 12, in which contact openings 8are made. After this, spacers 15 are attached to the surface of theconductor foil 12, to the future attachment points of the components 6and 26. The spacers 15 of the components 6 and 26 can be mutuallyidentical or selected component specifically, for example, in such a waythat the spacer 15 of the component 6 is of a different material and/orthickness to the spacer 15 of the component 26.

According to FIG. 18, manufacture is continued by spreading adhesivelayers 5 on the connection areas of the components and by laminatinginsulator sheets 10, 11 and a conductor foil 14 to the blank, exactly asdescribed in connection with FIG. 11. FIG. 19 show the module afterthese stages.

In the stage shown in FIG. 19, contact holes 18 are made at thepositions of the contact openings 8 of the component 6, as described inconnection with FIG. 13. At this stage, contact holes are not yet openedat the positions of the contact terminals 27 of the component 26.

The stage shown in FIG. 21 corresponds completely to the method stagedescribed in connection with FIG. 14. In this embodiment, anintermediate layer 2, which is of two layers, is manufactured in thecontact holes 18 of the component 6. In the example of the figure, thematerial of the contact terminals 7 of the component is aluminium. Thetwo-layer intermediate layer 2 of the example comprises first a grownlayer containing zinc and after this a grown nickel-aluminium layer. Thenickel-aluminium layer is grown by means of a chemical method and isused to seal the layer containing zinc.

Manufacture is continued in the stage shown in FIG. 22, by makingcontact holes 28 at the positions of the contact openings 8 of thesecond component 26. After this, according to FIG. 23 the module issubjected to a suitable chemical conductor-material growing method. Thisstage corresponds to the method stage described in connection with FIG.16. In the example of FIG. 23, the material of the surface of thecontact terminals 27 of the component 26 is copper and the material ofthe intermediate layer 2 grown of the surface of the contact terminalsis also copper.

FIG. 24, for its part, shows a modification of the embodiment of FIGS.18-23, in which, after the stage shown by FIG. 22, a first intermediatelayer is grown on top of the contact terminals 27 of the component 26,by means of a selective growing method and, after his, the growing ofthe intermediate layer 2 is continued using a non-selective method. Inthe example of FIG. 24, the material on the surface of the contactterminals 27 of the component 26 is gold and the material of theintermediate layer 2 grown on the surface of the contact terminals 27 isnickel.

In the embodiments of these FIGS. 18-24, after the manufacture of theintermediate layers 2 it is possible to continue, for example, by makingconductor patterns on the surface of the module and conductor cores forthe contact elements located in the contact holes 18 and 28, forexample, by means of the manner stated in connection with thedescription of FIGS. 6-9.

FIG. 25 shows in greater detail the shape of the contact hole andcorrespondingly also the shape of the contact element to be manufacturedin this opening. The example of FIG. 25 shows one possible shape, whichcan be achieved when using the embodiments described above. The shapecan be affected with the aid of the shape of the contact openings 8 tobe made in the conductor foil 12, the properties of the insulationbetween the conductor foil 12 and the component, and the operatingparameters of the CO₂ laser. The contact hole of FIG. 25 is rotationallysymmetrical and the cross-section shown in the figure is taken throughthe central axis of the contact hole, i.e. it shows the widest possiblecross-section. In FIG. 25, the size and shape of the contact hole aredetermined with the aid of the following parameters:

-   -   greatest width W _(MAX), from which the greatest cross-sectional        area A_(MAX) can be calculated,    -   the width W_(CONT) of the contact between the contact element        and the contact surface 7 of the component 6, from which the        contact surface-area A_(CONT 1) between the contact element and        the contact surface of the component can be calculated, and    -   the width W_(HOLE) of the contact opening, from which the        contact surface-area A_(CONT 2) between the contact element and        the conductor of the conductor-pattern layer can be calculated.

The figure also shows the width W_(PAD) of the contact surface of thecomponent, from which the surface area A_(PAD) of the contact surfacecan be calculated, if the shape of the contact surface is known. Thecontact surface 7 can be, for example, square in shape and, when W_(PAD)represents the width of a side, the surface area of the contact surfaceis obtained as: A_(PAD)=W_(PAD)×W_(PAD). Of course, the surface areascan also be determined with the aid of surface-area measurement, whichcan be more practical if the surface area to be determined is of anirregular shape.

In the figure, the contact surface 7 is surrounded by a passivationlayer 9 made on the surface of the component 6. In that case, thesurface area A_(PAD) refers precisely to the surface area free to form acontact, i.e. the surface area of the surface that is revealed in theopening made in the passivation layer 9. In addition, the figure showsthe distance H of the distance between the conductor foil 12 and thecontact surface 7, which corresponds to the depth of the contact holeand is thus the height of the contact element to be made in the contacthole. Because the contact hole is filled entirely with conductormaterial, the other dimensions too of the contact hole correspond to thedimensions of the contact element and the parameters W_(MAX) andW_(HOLE) can also be used to refer to the corresponding dimensions ofthe contact element.

The following presents some typical parameters in connection with theembodiments described above:

-   -   H=1-50 μm, usually 5-30 μm;    -   W_(PAD)=20-1000 μm, usually 50-200 μm, and most usually about        100 μm; and    -   W_(HOLE)=5-500 μm, usually 20-75 μm, and most usually about        30-50 μm.

In addition, generally W_(HOLE)≧H, which represents the reliable fillingof the contact hole. The contact hole 18 is intended to be manufacturedin such a way that the side walls of the hole would be vertical. Inother words, the goal is a contact hole, the width and shape of whichremains constant over the whole distance H between the conductor foil 12and the contact surface 7, i.e. the contact hole would have the shape ofthe contact opening 8 over all of this distance. A shape that narrowstowards the contact surface 7 is also good. In practice, when using thelaser process described above the contact hole can, however, becomewidening towards the contact surface 7, or first widening and thennarrowing, so that the contact hole is widest somewhere between theconductor foil 12 and the contact surface 7. FIG. 25 shows a contacthole of this kind Such a non-optimal shape is not problematic, providedthe widening is not too great and the filling of the hole succeeds well.

Of the dimension values of the widths referred to above, the widthW_(PAD) of the contact surface 7 of the component is determined throughthe selection of the component. If necessary, W_(PAD) can be measuredseparately from each straight line that runs through the centre point ofthe contact surface 7. This definition may be required when examiningthe dimension values referred to above and their ratios, if the shape ofthe contact surface 7 or of the contact opening 8 is irregular. In themost usual cases, the contact surface is, however, square, in which casethe width of the side of the square can generally be used as the widthW_(PAD) of the contact surface 7.

The width W_(HOLE) of the contact opening 8 is a parameter, which isselected when planning the manufacturing process. One parameter to betaken into account when selecting the width of the contact opening 8 isthe width of the contact surface 7 of the component being used. Thewidth of the contact opening 8 is selected in such a way that thecontact hole to be made through the contact opening will meet thecontact area 7 of the component over its entire cross-sectional area arethe component end, and will not miss the contact area, for example, onthe surface of the passivation layer. If the contact opening is circularin shape, with width W_(HOLE) of the contact opening is the diametermeasured through the centre point of the circle. If, on the other hand,the contact opening is irregular I shape, W_(HOLE) can, if necessary, bemeasured separately along each straight line that runs through thecentre point of the contact opening 8. In the case of an irregularshape, when comparing the width W_(HOLE) of the contact opening with thewidth W_(PAD) of the contact surface, the comparison can always be madeseparately for each pair of widths measured through parallel straightlines. If necessary, the widths W_(HOLE) and W_(PAD) can also becompared in a corresponding manner to the other parameters described.

The ratios of the parameters described above can also be applied inconnection with the contact bumps 17, in which case the surface area andwidth of the contact area will be replaced by the surface area and widthof the contact bump and the distance H will be measured to the surfaceof the contact bump.

The shape of the contact hole can be influenced with the air of thelaser parameters, which are selected according to the hole parametersand the properties of the insulation to be removed. The manufacturingresult is, of course, also affected by the laser device being used. Thesuitability of the selected parameters for the process is indeedexamined with the aid of a pilot manufacturing batch and, if necessary,the parameters are altered so that the desired result will be achieved.

In general, it is sensible in the manufacturing method to try to achievea contact-hole shape, in which

-   -   W_(CONT)=0.5-1.5 times W_(HOLE), preferably 0.7-1.2 times        W_(HOLE), and most preferably 0.8-1.0 times W_(HOLE), however,        in such a way that W_(CONT)<W_(PAD); and    -   W_(MAX)=at most 100 μm, preferably at most 30 μm, and most        preferably at most 10 μm larger than whichever of the parameters        W_(HOLE) and W_(CONT) is greater. Presented relatively, the        objective would be for W_(MAX)=at most 40%, preferably at most        20%, and most preferably at most 10% greater than whichever of        the parameters W_(HOLE) and W_(CONT) is greater.

In the most optimal shape of a contact element, W_(MAX) is essentiallyas large as W_(HOLE) and, in addition, W_(CONT) is 0-20% smaller thanW_(MAX).

In the most typical embodiments, the contact surface 7 has a squareshape and the contact opening 8 is circular in shape. In that case,A_(CONT 1) is typically 10-75% of the surface area A_(PAD)). A_(CONT 1)and A_(CONT 2) are typically mutually approximately of equal size, forexample, with an accuracy of ±20%.

FIG. 26 shows examples of other possible shapes of the contact holes 18.FIG. 27, for its part, shows examples of intermediate layers 2manufactured in such contact holes. In the examples of FIGS. 26 and 27,the component to be attached is bumpless. As can be seen from FIG. 27,the intermediate layers 2 do not extend at all on top of the passivationlayer 9 of the component, but instead are in contact only with thecontact surface 7 of the component. With the aid of this feature, it ispossible to see even from the finished electronic module whether thecomponent embedded in the electronic module has bumps or is bumpless.The bumps grown on the contact surface 7 of the component in thebump-creation processes always fill the entire contact surface 7 andalways also spread slightly on top of the passivation layer 9. If, onthe other hand, bumpless components are used in the embodimentsdescribed above, the intermediate layer 2 and the contact element growonly into the contact hole 18, when in the finished electronic modulethe intermediate layer 2 will not extend on top of the component'spassivation layer 9 and part of the contact surface 7 of the componentwill always remain free of the intermediate layer 2 (the edges of thecontact surface 7) when the alignment and manufacture of the contacthole 8 have succeeded. Also in a possible contact-hole 18alignment-error situation, in which the contact opening 8 is notcompletely aligned with the contact surface 7, at least part of the edgeareas of the contact surface 7 and of the passivation layer surroundingthe edge area will be free of the intermediate layer 2.

If a bumpless component is manufactured by a semiconductor process usingcopper conductors, the contact area 7 is copper. In that case, theintermediate layer can be manufactured directly from chemically growncopper, which forms a conductor surfacing also on the side walls of thecontact hole 18. After this, the contact holes 18 can be filled and thethickness of the conductor layer increased using an electrochemicalcopper-growing method.

At the moment of writing of the present application, the most commonlyused conductor material in semiconductor processes is, however,aluminium. Thus, the most common material of the contact area 7 ofbumpless components too is aluminium and it is preferable to use anintermediate layer, with one or more layers manufactured from differentmaterials, between the aluminium contact area and the copper conductorsof the electronics module. In the following, reference is made to a fewpossible intermediate- layer constructions:

Intermediate-Layer Construction 1

First of all, a layer containing zinc is grown on the surface of thealuminium contact area 7. The layer containing zinc manufactured by azincate process does not grow on the polymer surfaces of the side wallsof the contact hole 18. A layer of nickel, which does not grow at all oronly poorly on a polymer surface, is grown by a chemical method on thesurface of the layer containing zinc. A layer of copper is grown by achemical method on the surface of the nickel. The copper grown by achemical growing method can be made to grow reliably also on top ofpolymer, thus making the side walls of the contact holes 18 conductivefor later electrochemical growing.

Intermediate-Layer Construction 2

First of all, a layer containing zinc is grown on the surface of thealuminium contact area 7. The layer containing zinc manufactured by azincate process does not grow on the polymer surfaces of the contacthole 18. A layer of copper is grown by a chemical method on the surfaceof the layer containing zinc. The copper grown by a chemical growingmethod can be made to grow reliably also on top of polymer, thus makingthe side walls of the contact holes 18 conductive for laterelectrochemical growing.

Intermediate-Layer Construction 3

First of all, a layer containing zinc is grown on the surface of thealuminium contact area 7. The layer containing zinc manufactured by azincate process does not grow on the polymer surfaces of the contacthole 18. A layer of nickel-aluminium, which does not grow on a polymersurface, is grown by a chemical method on the surface of the layercontaining zinc. A layer of copper is grown by a chemical method on thesurface of the nickel-aluminium. The copper grown by a chemical growingmethod can be made to grow reliably also on top of polymer, thus makingthe side walls of the contact holes 18 conductive for laterelectrochemical growing.

Intermediate-Layer Construction 4

First of all, a layer containing zinc is grown on the surface of thealuminium contact area 7. A layer of nickel-aluminium is grown by achemical method on the surface of the layer containing zinc. A layer ofnickel is grown by a chemical method on the surface of thenickel-aluminium and a layer of copper is grown by a chemical method onthe surface of the nickel.

Intermediate-Layer Construction 5

First of all, a layer containing zinc is grown on the surface of thealuminium contact layer 7. A layer of nickel is grown by a chemicalmethod on the surface of the layer containing zinc.

Intermediate-Layer Construction 6

A layer of nickel is grown by a chemical method on the surface of thealuminium contact area 7, which grown nickel layer alone forms theintermediate layer 2.

Intermediate-Layer Construction 7

A layer of nickel is grown by a chemical method on the surface of thealuminium contact area 7, and a layer of copper is grown by a chemicalmethod on the surface of the nickel.

In the above examples of intermediate-layer constructions, the layercontaining zinc contains, for example, about 80% zinc, about 16% copper,about 2-3% nickel, and about 2-3% iron. This is only one possibleexample of alloy ratios suitable for the application, so that the alloyratios can, of course, vary according to the applications. In the aboveexamples of intermediate constructions, the thickness of the layercontaining zinc is less than 1 μm, usually as a single layer about 0.1μm and as several layers, for example 0.3-0.4 μm. At its thinnest, thelayer containing zinc can be about 5-10 nm after manufacture. Whengrowing a layer containing nickel or nickel-aluminium on top of thelayer containing zinc, at least some of the zinc atoms dissolve and arereplaced with nickel atoms. In the finished circuit module, it can bepossible for the layer containing zinc to be observable as mainly aconcentration profile of zinc in the interface between the aluminium andthe material of the next layer. The layer containing zinc need notnecessarily be precisely limited in the final product, because the zinccan diffuse to the adjacent material layers, particularly in stages ofthe manufacturing process using higher temperatures.

In one preferred embodiment, the layer containing zinc is grown by adouble zincate process. With a single zincate process, the zinc forms anon-uniform and uneven surface on top of the aluminium. The adhesion ofa nickel layer grown on top of such a surface is weaker and is lesssuitable for use with small micro-via openings. The quality of the grownzinc surface can be significantly improved by using a double zincateprocess. Typically, in such a process, after the first zincatetreatment, the layer containing zinc is stripped using nitric acid(HNO₃), after which a second layer containing zinc is coated. By meansof the double zincate process, a tight and uniform layer containing zincis obtained on the surface of the component's aluminium junctioninterface.

The thickness of the nickel-aluminium layer, for its part, can be, forexample, 0.2-2 μm. The thickness of the nickel layer, on the other hand,can be, for example 0.5-20 μm, typically 2-10 μm. The layer thicknessestoo are only examples of the possible layer thicknesses and other layerthicknesses can also be used.

In the embodiments, the electrochemically grown copper layer can have athickness of, for example, 5-30 μm, typically 10-20 μm. The copper layergrown by a chemical growing method, for its part, is generallymanufactured to be clearly thinner, and its thickness in the embodimentsis, for example, 0.1-2 μm, typically 200-800 nm.

In the manufacturing methods described above, it is, of course, alsopossible to use intermediate-layer constructions and materials, forexample tin, other than those referred to above. It is also possible togrown a nickel layer directly on the surface of the aluminium, forexample, by alkali etching and flushing the surface after this withpropan-2-ol and immediately after this coating with propan-2-ol atboiling point in a warm chemical nickel bath. In addition, the surfaceof the layer containing zinc could also be coated with chromium and goldon the surface of the nickel.

FIG. 28 shows yet another possible contact structure, in which it ispossible to use components, the contact area of which is pre-equippedwith base-metallurgical layers, though bumps as such are not made. FIG.29 shows one possible corresponding contact structure, implemented witha bumpless component.

FIG. 28 shows a passivation layer 9 on the surface of the component, inwhich there is an opening at the position of the contact area 7 of thecomponent. There is a polymer layer 25 of the surface of the passivationlayer 9. The polymer layer 25 can consist of one or more polymer layers.The material of the polymer layer 25 can contain, for example, aninsulator layer 13 depicted in connection with FIG. 1, adhesive 5depicted in connection with FIG. 2, and/or a spacer depicted inconnection with FIG. 11. The base metallurgy, which in this casecomprises two layers, is made on the surface of the contact area 7 ofthe component. The first base-metallurgy layer 26 is a layer of, forexample, chromium (Cr) or titanium-wolfram (TiW) manufactured bysputtering. The second base-metallurgy layer 27 is a layer of, forexample, nickel (Ni), copper (Cu), or gold (Au), manufactured bysputtering. The actual bump comprises further a gold or copper layer,for example, grown chemically or electrochemically, on the surface ofthe second base-metallurgy layer 27.

In the example of FIG. 28, the component is attached by a polymer layer25 to a conductor foil 12, in which contact openings 8 have been made asdepicted in the methods described above. Contact holes 18 or 28, inwhich a contact element is made in contact with the secondbase-metallurgy layer 27, are made through the contact openings 8. Thecontact element is made in such a way that first of all an intermediatelayer 2 is made using one or more chemical growing methods, in acorresponding manner to that depicted in the methods described above. Inthe example of FIG. 28, the intermediate layer 2 is of copper grownusing a chemical growing method. On top of this intermediate layer alayer 32 of copper is grown using an electrochemical growing method. Theelectrochemically grown copper also forms the conductor core 29 of thecontact element. It can be seen from FIG. 28 that the conductor foil 12,the intermediate layer 2, and the copper layer 32 together form thematerial of the conductor 22. In the example, the conductor foil 12, theintermediate layer 2, and the copper layer 32 are all of copper, but thelayers and the interfaces between them, can, however, also be detectedby analysing the finished structure.

Like FIG. 28, FIG. 29 shows a passivation layer 9, in which there is anopenings at the position of the contact area 7 of the component, on thesurface of the component. On the surface of the passivation layer 9 is apolymer layer 25, which corresponds to that shown in connection withFIG. 28. In the example of FIG. 29, the surface of the contact area 7 ofthe component has been a uncoated component when it was brought to thecircuit-module manufacturing process. In such a component, the outersurface of the contact area 7, i.e. the contact surface, is thustypically formed already at the semiconductor factory. In the example ofFIG. 29, the material of the contact area 7 is aluminium.

In the example of FIG. 29, the component is attached by a polymer layer25 to the conductor foil 12, in which contact openings 8 are made in themanner depicted in the methods described above. Contact holes 18 or 28,in which a contact element is made in contact with the contact area 7,have been made through the contact openings 8. The contact element ismade in such a way that first of all an intermediate layer 2 is madeusing one or more chemical growing methods, in a corresponding manner tothat described above. In the example of FIG. 29, the intermediate layer2 is made in several parts and comprises several layers. In FIG. 28, theintermediate layer is, in addition, to facilitate the description,divided into three parts, a base part 36, a wall part 37, and aconductor part 38. The base part 36 is the part that grows on thesurface of the contact terminal 7, 17 to the bottom of the contact hole18, 28, the wall part 37 is the part that grows on the surfaces of theside walls of the contact hole 18, 28, and the conductor part 38 is thepart that grows to form part of the conductor 22 being manufactured.

The intermediate layer 2 of FIG. 29 comprises a first intermediate layer33, a second intermediate layer 34, and a third intermediate layer 35.The first intermediate layer 33 can be made, for example, by using achemical growing method to grow a layer containing zinc. In the exampleof FIG. 29, the conductor foil 12 is of copper, so that when using azincate process the first intermediate layer 33 grows only on the basepart 36 of the intermediate layer 2. From this, manufacture can becontinued, for example, by using a chemical nickel-growing method tomake the second intermediate layer 34. The nickel grows on both the basepart 36 and the conductor part 38 of the intermediate layer and, whenusing some growing methods, on the wall part 37 too on the surface ofthe polymer 25. The third intermediate layer 35 is made from copper ontop of the second intermediate layer 34 using a chemical growing method,so that the copper grows on the base part 36, the wall part 37, and theconductor part 38. A layer 32 of copper is grown on top of the thirdintermediate layer using an electrochemical growing method, which alsoforms the conductor core 29 of the contact element.

In the case of FIG. 29, it should be noted that, in the finished circuitmodule, the layers 33 and 34 do not have precise boundaries as shown inthe figure, but instead the layers can appear as overlapping or mixed,for example, from the effect of diffusion. For example, in the case ofthe first intermediate layer 33 containing zinc, the zinc can be locatedas a concentration profile in the interface between the aluminium andnickel 34 and partly inside the aluminium 7 and the nickel layer 34.

In the contact structure of FIG. 29, other material combinations canalso be used. For example, suitably selected intermediate-layerstructures from the intermediate-layer constructions 1-7 described abovecan be used to form the contact structure depicted by

FIG. 29 and also the contact structures depicted by FIGS. 30-33. Inaddition, the contact structure of FIG. 29 can also be manufactured withthe aid of the materials shown by FIG. 28, in such a way that the firstintermediate layer 33 and the second intermediate layer 34 are made bysputtering. In that case, the sputtered intermediate layers 33 and 34will grow to the base part 36 and the conductor part 38, but not to anysubstantial extent to the wall part 37, provided the contact hole 18, 28does not widen towards the contact opening 8. One possibility is to usea first intermediate layer 33 containing zinc and on the surface of thiseither directly a third intermediate layer 35 made from nickel by achemical growing method, or a construction, in which a secondintermediate layer 34 made from nickel-aluminium is used between thelayers 33 and 35.

In such an embodiment, there is no need at all of chemical coppergrowing, as the nickel forms a vertical contact along the side wall ofthe contact hole.

FIG. 30 shows yet another contact-element structure. In the structure ofFIG. 30, the intermediate layer 2 comprises a first intermediate layer33, a second intermediate layer 34, and a third intermediate layer 35.The first intermediate layer 33 can be made, for example, by using achemical growing method to grow a layer containing zinc. The secondintermediate layer 34 is of nickel-aluminium and the third intermediatelayer 35 is of nickel grown by a chemical growing method. This, in thestructure of FIG. 30, the contact hole is filled with nickel, i.e. theconductor core 29 of the contact element is nickel. Otherwise, thetechnical features described in connection with FIGS. 28 and 29 apply inthe case of the structure of FIG. 30.

FIG. 31 shows yet another contact-element structure. In the structure ofFIG. 31, the intermediate layer 2 comprises a first intermediate layer33 and a second intermediate layer 34. The first intermediate layer 33can be manufactured, for example, by using a chemical growing method togrow a layer containing zinc. The second intermediate layer 34 is ofcopper grown by a chemical growing method, or alternatively of nickelgrown by a selective chemical growing method. Alternatively, thestructure of FIG. 31 can also be made in such a way that the first andsecond intermediate layers 33 and 34 are replaced with a single layer ofchemically grown nickel. The conductor core 29 is typically copper andthe conductor 22 comprises a first and second copper layer 12 and 32.Otherwise the technical features described in connection with FIGS. 28and 29 apply in the case of the structure of FIG. 31.

FIG. 32 shows yet another contact-element structure. In the structure ofFIG. 32, the intermediate layer 2 comprises a first intermediate layer33, a second intermediate layer 34, and a third intermediate layer 35.The first intermediate layer 33 can be made, for example, by using achemical growing method to grow a layer containing zinc. The secondintermediate layer 34 is of nickel grown by a chemical growing method.In the method, the growing method is selective, in such a way that thenickel grows on top of conductive material. The third intermediate layer35 is of copper grown by a chemical growing method. Alternatively, thestructure of FIG. 32 can also be made in such a way that the firstintermediate layer 33 is omitted. The conductor core 29 is typically ofcopper. Otherwise the technical features described in connection withFIGS. 28 and 29 apply in the case of the structure of FIG. 32.

FIG. 33 shows yet another contact-element structure. The methoddescribed in connection with FIGS. 10-17, for example, in which aphoto-resist layer 30 is used, can be used for making the structure ofFIG. 32. In the structure of FIG. 33, the intermediate layer 2 comprisesa first intermediate layer 33, a second intermediate layer 34, and athird intermediate layer 35. The first intermediate layer 33 can bemade, for example, by using a chemical growing method to grow a layercontaining zinc. The second intermediate layer 34 is of nickel grown bya chemical growing method. In the method of the example, the growingmethod is selective, in such a way that the nickel grows only on top ofconductive material. The third intermediate layer 35 is of copper grownby a chemical growing method. Alternatively, the structure of FIG. 33can also be made in such a way that the first intermediate layer 33 isomitted. The conductor core 29 is typically of copper. Otherwise thetechnical features described in connection with

FIGS. 28 and 29 apply in the case of the structure of FIG. 33.

Thus, in the embodiments a method is presented for the manufacture of acircuit module, in which method

-   -   a conductor foil 12 is taken,    -   a component 6, which comprises contact areas 7, the material of        which contains a first metal, is taken,    -   the component 6 is attached to a conductor foil 12 by means of a        polymer layer 25,    -   an insulator layer 1 is manufactured around the component 6        attached to the conductor foil 12,    -   contact holes 18, 28 are made in the polymer layer 25 at the        positions of the contact areas 7, in such a way that the contact        surface area A_(CONT 1) between each contact hole 18, 28 and the        corresponding contact area 7 is less that the surface area        A_(PAD) of the contact area 7, and    -   an intermediate layer 2, which contains at least a third metal,        is grown at least on the surface of the contact areas 7 in the        contact holes 18, 28, and    -   a layer 32 of a second metal is grown, which layer 32 is in        contact with the surface of the intermediate layer 2 and extends        along the conductors 22 being made, and    -   conductors 22 are formed by patterning the conductor foil 12,        and, if necessary, also the intermediate layer 2 on the surface        of the conductor foil 12 and/or the layer 32 of a second metal.

In a typical embodiment, the contact holes 8 are made in the conductorfoil 12 before attaching the component, so that the component is thusattached to a conductor foil 12 equipped with contact openings. In thecommonest form of this type of embodiment, the contact openings do notextend to the surfaces of the contact areas 7, so that after theattaching of the component 6 contact holes 18, 28 are further openedthrough the contact openings 8.

In one embodiment, the first metal is aluminium, the second metal iscopper, and the third metal is zinc. In such an embodiment, theintermediate layer 2 can, of course, in addition to zinc, also containother metals or metal alloys, as stated above.

In a second embodiment, the first metal is aluminium, the second metalis copper, and the third metal is nickel. In such an embodiment, theintermediate layer 2 can, of course, in addition to nickel, also containother metals or metal alloys, as stated above.

In a third embodiment, the first metal is gold, the second metal iscopper, and the third metal is nickel. In such an embodiment, theintermediate layer 2 can, of course, in addition to zinc, also containother metals or metal alloys, as stated above.

In the commonest embodiment, the material of the contact areas 7 ismainly aluminium and the material of the conductors is copper andbetween them is one of the intermediate-layer constructions 1-7described above.

When making the intermediate-layer construction, at least one chemicalgrowing method is typically used.

The embodiments depict a circuit module, which comprises

-   -   an insulator layer 1,    -   inside the insulator layer 1, at least one component 6, which        comprises contact areas 7, the material of which contains a        first metal,    -   on the surface of the insulator layer 1, conductors 22, which        comprise at least a first layer 12 and a second layer 32, in        such a way that at least the second layer 32 contains a second        metal, and    -   contact elements for forming electrical contacts between the        contact areas 7 and the conductors 22, which contact elements        comprise an intermediate layer 2, which contains a third metal,        on the surface of the material of the contact area 7,    -   in which the first, second, and third metals are different        metals, and    -   the contact surface area A_(CONT 1) between the intermediate        layer 2 and the contact area 7 is less than the surface area        A_(PAD) of the contact area.

In one embodiment, the first metal is aluminium, the second metal iscopper, and the third metal is zinc. In such an embodiment, theintermediate layer 2 can, of course, in addition to zinc, also containother metals or metal alloys, as stated above.

In a second embodiment, the first metal is aluminium, the second metalis copper, and the third metal is nickel. In such an embodiment, theintermediate layer 2 can, of course, in addition to nickel, also containother metals or metal alloys, as stated above.

In a third embodiment, the first metal is gold, the second metal iscopper, and the third metal is nickel. In such an embodiment, theintermediate layer 2 can, of course, in addition to nickel, also containother metals or metal alloys, as stated above.

In the commonest embodiment, the material of the contact areas 7 ismainly aluminium and the material of the conductors is copper andbetween them is one of the intermediate-layer constructions 1-7described above.

In a typical embodiment, the contact elements comprise a copper core 29made using an electrochemical growing method, which, in the direction ofthe side walls and the component 6 is bounded by the intermediate layer2 and in the direction of the conductor 22 connects continuously, i.e.without an interface to the material of the second layer 32 of theconductor 22. In order words, the material of the copper core 29 of thecontact element and of the second layer 32 of the conductor 22 ismanufactured in the same process, so that the parts are attachedpermanently to each other and there is no interface between them.Between the first layer 12 and second layer 22 of the conductor, on theother hand, there is typically an interface, or a correspondingtransition zone, which can be detected, for example, by analysing thecrystalline structure or impurity concentration of the metal.

In one embodiment, the width W_(CONT) of the contact surface between thecontact element and the contact area 7 of the component is 0-20% lessthan the greatest width W_(MAX) of the contact element in the samedirection.

The contact elements usually fill entirely the contact holes 18, 28,i.e. the contact elements are not hollow, but are solidly of conductormaterial.

Usually, the aim in the embodiments is for the height H of the contactelement to be less than, or equal to the greatest width W_(MAX) of thecontact element.

There are also embodiments of the circuit module, in which the insulatorlayer 1 includes at least one layer of fibre material 19, in which thereis an opening in the fibre material 19 for the component 6, as well as auniform polymer layer, which is attached to the fibre material 19 and tothe components 6, 16.

The manufacturing processes described above and their sub-processes canbe modified in many ways. For example, the use of an actual adhesivedepicted above in attaching the component to the conductor foil 12 canbe replaced with some other adhesion mechanism. On example that can begiven is the use of an insulator layer 13 possessing an adhesionproperty on the surface of the conductor foil 12 (see FIG. 1 and thecorresponding description). The components 6 are then pressed directlyagainst the insulator layer 13, so that the components attachsufficiently in place in a manner correspondingly to that described inconnection with the embodiment using adhesive. Such an insulator layer13 can contain, for example, a tape-like surfacing, or consist of apolymer or similar material that is shapable at least in its surfacepart.

The method can also be implemented without the use of an adhesive 5 oran adhesion property. In that case, the components 6 can be attached inplace, for example, mechanically or with the aid of a vacuum. The vacuumor similar temporary attachment can then be maintained until thecomponent 6 is sufficiently secured in place with the aid of theinsulator material 1.

The component 6 to be attached can be, for example, an integratedcircuit, such as a memory chip, processor, or ASIC. The component to beattached can also be, for example, a MEMS, LED, or passive component.The component to be attached can be cased or uncased and its contactterminals can consists of contact areas 7, contact bumps 17, or similar.There can also be a conductor coating thinner than an actual contactbumb on the surface of the contact areas of the component.

A different material of the insulator layer 1 from those in the examplesdescribed above can also be selected. The insulator layer 1 can bemanufactured from a suitable polymer or from a material containingpolymer. The material of manufacture of the insulator layer 1 can be,for example, in a liquid or pre-hardened form (such as prepreg). In themanufacture of the insulator layer 1 it is possible to use, for example,glass-fibre reinforced sheet, such as an FR4 or FR5-type sheet. Otherexamples of materials, which can be used in the manufacture of theinsulator layer 1 are PI (polyimide), aramide, polytetrafluoroethylene,and Teflon®. Instead of, or as well as thermosetting plastics,thermoplastics too, for example some suitable LCP (liquid crystalpolymer) material can be used in the manufacture of the insulator layer1.

In addition, it is obvious to one skilled in the art that the featuresdescribed above of the invention can be used as part of some largertotality, for example, in such a way that the electronics module ismanufactured partly using some method according to the prior art andpartly using the embodiments depicted here. It is also possible tomanufacture additional circuit-board layers on the surface or surfacesof the electronic-module structures described above, or also to attachcomponents, for example, by means of the surface-mounting technique.

One skilled in the art will also understand that, when reference is madein the present document to a specific material, for example, aluminium,nickel, or copper, the reference is to a material, which in terms of theapplication is substantially of the said material. The material referredto can thus, in addition to the said principal element contain, from thepoint of view of the application, insubstantial amounts of impuritiesand other elements. For example, an aluminium contact area is usually ofa material that typically contains a minimum of 95% aluminium.

When, on the other hand, reference is made to a material containing somespecific element, this means that the material contains an essentiallylarge content of the said element. In addition, the material can containsubstantial or insubstantial amounts of other elements. For example, thelayer containing zinc will thus contain an amount of zinc that is ofsignificance in terms of the contact properties between the aluminiumand the next metal.

The examples given above depict some possible methods and structures,which the aid of which our invention can be exploited. However, ourinvention is not restricted to only the examples and embodimentsdescribed above, but instead the invention covers numerous other methodsand structures, taking into account the full scope of the Claims and theequivalence interpretation.

1. A circuit module, comprising an insulator layer; at least one firstcomponent inside the insulator layer, the at least one first componentcomprising first contact terminals with contact surfaces of first metal;at least one second component inside the insulator layer, the at leastone second component comprising second contact terminals with contactsurfaces of second metal different from the first metal; conductors on asurface of the insulator layer, the conductors comprising at least afirst layer of copper and a second layer of copper; first contactelements for forming first electrical contacts between the first contactterminals and the conductors, the first contact elements comprising anintermediate layer on each contact surface of the first contactterminal, the intermediate layer containing a third metal different fromthe first metal, a contact surface area (A_(CONT 1)) between theintermediate layer and the contact terminal being less than a surfacearea (A_(PAD)) of the contact surface of the first contact terminal; andsecond contact elements for forming second electrical contacts betweenthe second contact terminals and the conductors, a contact surface area(A_(CONT 1)) between each second contact element and the respectivesecond contact terminal being less than a surface area (A_(PAD)) of thecontact surface of the second contact terminal.
 2. The circuit module ofclaim 1, wherein the second contact elements comprise an intermediatelayer on each contact surface of the second contact terminal, theintermediate layer containing a fourth metal different from the secondmetal.
 3. The circuit module of claim 1, wherein the first metal isaluminium.
 4. The circuit module of claim 3, wherein the third metalcomprises at least one of zinc and nickel.
 5. The circuit module ofclaim 1, wherein the second metal is copper.
 6. The circuit module ofclaim 1, wherein the first metal is aluminium and the second metal iscopper.
 7. The circuit module of claim 6, wherein the third metalcomprises at least one of zinc and nickel.
 8. The circuit module ofclaim 1, wherein the intermediate layer extends along the side walls ofthe first contact elements between the first contact terminals and theconductors.
 9. The circuit module of claim 1, wherein each contactelement comprises a copper core, which connects continuously to thematerial of the second layer of the conductors.
 10. The circuit moduleof claim 1, wherein the conductors comprise a first layer of copper onthe surface of the insulator layer; and a second layer of copper on thesurface of the first copper layer.
 11. The circuit module of claim 1,wherein the conductors comprise a first layer of copper on the surfaceof the insulator layer; an intermediate layer on the surface of thefirst copper layer; and a second layer of copper on the surface of theintermediate layer.
 12. The circuit module of claim 1, wherein a width(W_(CONT)) of the contact surface between the contact element and thecontact terminal of the component is 0-20% less than a greatest width(W_(MAX)) of the contact element in the same direction.
 13. The circuitmodule of claim 1, wherein a height (H) of the contact element is lessthan, or equal to a greatest width (W_(MAX)) of the contact element. 14.A circuit module, comprising an insulator layer; at least one firstcomponent inside the insulator layer, the at least one first componentcomprising first contact terminals with contact surfaces made ofaluminium; at least one second component inside the insulator layer, theat least one second component comprising second contact terminals withcontact surfaces made of copper; conductors on a surface of theinsulator layer, the conductors comprising at least a first layer ofcopper and a second layer of copper; first contact elements for formingfirst electrical contacts between the first contact terminals and theconductors, the first contact elements comprising an intermediate layeron each contact surface of the first contact terminal, a contact surfacearea (A_(CONT 1)) between the intermediate layer and the contactterminal being less than a surface area (A_(PAD)) of the contact surfaceof the first contact terminal; and second contact elements between thesecond contact terminals and the conductors for forming secondelectrical contacts, a contact surface area (A_(CONT 1)) between eachsecond contact element and the respective second contact terminal beingless than a surface area (A_(PAD)) of the contact surface of the secondcontact terminal.
 15. The circuit module of claim 14, wherein theintermediate layer comprises at least one of zinc and nickel.
 16. Thecircuit module of claim 14, wherein the first contact terminals arecontact areas on a surface of a semiconductor component, a surface ofeach contact area revealed in an opening made in a passivation layermade on the surface of the semiconductor component.
 17. The circuitmodule of claim 14, wherein the second contact terminals are contactbumps made on contact areas on a surface of a semiconductor component.18. The circuit module of claim 14, wherein the second contact terminalsare contact areas on a surface of a semiconductor component, a surfaceof each contact area revealed in an opening made in a passivation layermade on the surface of the semiconductor component.
 19. A circuitmodule, comprising an insulator layer; at least one first semiconductorcomponent inside the insulator layer, the at least one firstsemiconductor component comprising first contact terminals, the firstcontact terminals being contact areas on a surface of the semiconductorcomponent, a surface of each contact area revealed in an opening made ina passivation layer made on the surface of the semiconductor component;at least one second semiconductor component inside the insulator layer,the at least one second semiconductor component comprising secondcontact terminals, the second contact terminals being contact bumps madeon contact areas on a surface of the semiconductor component; conductorson a surface of the insulator layer, the conductors comprising at leasta first layer of copper and a second layer of copper; first contactelements for forming first electrical contacts between the first contactterminals and the conductors, the first contact elements comprising anintermediate layer on each contact surface of the first contactterminal, the intermediate layer containing a metal different from ametal of the first contact terminal, a contact surface area (A_(CONT 1))between the intermediate layer and the contact terminal being less thana surface area (A_(PAD)) of the contact surface of the first contactterminal; and second contact elements for forming second electricalcontacts between the second contact terminals and the conductors, acontact surface area (A_(CONT 1)) between each second contact elementand the respective second contact terminal being less than a surfacearea (A_(PAD)) of the contact surface of the second contact terminal.20. The circuit module of claim 19, wherein the metal of the firstcontact terminal is aluminium and the intermediate layer comprises atleast one of zinc and nickel.